JP2023539517A - Reversible pneumatically driven expander - Google Patents

Abstract

Pneumatically driven cryogenic refrigerators, which are mainly operated on the Gifford-McMahon (GM) cycle, are switched from cooling to heating by a switching valve between a rotary valve that reciprocates a displacer and a drive piston. The rotary valve has ports at two radial locations, one that circulates flow to the displacer and one that circulates flow to the drive piston. Two ports circulate flow to the top of the drive piston, the "cooling" port optimizing the cooling cycle and the "warming up" port providing a good heating cycle. Diversion valves that change flow from one port to another can be operated linearly or rotationally. Rotary valves do not rotate in reverse. [Selection diagram] Figure 1

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63/071,669, filed August 28, 2020, which is incorporated herein by reference in its entirety.

The present invention relates to a pneumatic drive mechanism for a reciprocating cryogenic expander that includes a built-in valve for switching between cooling and heating.

Semiconductors are manufactured in a vacuum chamber, which typically uses a cryopump cooled by a Gifford-McMahon (GM) type refrigerator to create a vacuum. A cryopump has a warm panel cooled to about 80 K, where Group I gases such as water vapor freeze, and a cold panel cooled to about 20 K, where Group II gases such as nitrogen and oxygen freeze. The charcoal behind the cold panel absorbs lighter gases such as hydrogen and helium. After a few days or weeks of operation, the cryopump needs to be warmed up to remove cryodeposits. Because flammable gases can accumulate inside the cryopump, heaters are avoided in the cryopump, and the cryopanel is usually heated indirectly by a heater located outside the cryopump housing. It will be done. The GM type expanders currently in use provide cooling when moved in one direction, and decrease the degree of cooling when moved in the opposite direction. The use of a cryopump with an expander that can be heated alternately provides the option of faster warm-up and/or lower cost.

W. E. Gifford and H. O. The GM cycle is disclosed in US Pat. No. 3,045,436 to McMahon. The systems disclosed herein operate primarily on the GM cycle and typically have input power in the range of 5-15 kW, although larger and smaller systems are also within the scope of this invention. Refrigerators based on the GM cycle and many Brayton cycles use oil-lubricated compressors designed for air conditioning applications to supply gas (helium) to reciprocating cryogenic expanders. GM expanders circulate gas through room temperature inlet and outlet valves and a regenerator to a cold expansion space, whereas Brayton cycle expanders circulate gas in and out of the cold expansion space at room temperature. It has an exchanger and cold inlet and outlet valves for circulating gas to a cold expansion space. The expander displacer is mechanically or pneumatically driven.

U.S. Pat. No. 3,205,668 to Gifford discloses a GM expander having a stem attached to the warm end of the displacer, the stem being driven by a rotary valve that controls pressure above the stem. The displacer is driven up and down by circulating it out of phase with the pressure to the expansion space. If the valve is rotating in the forward direction, it is assumed that the displacer is lowered (minimum cold displaced volume) and the cycle begins with lower pressure and higher pressure above the stem. Ru. When the pressure on the displacer switches to high pressure, the drive stem pressure switches to low pressure after a short delay. This causes the displacer to rise, forcing high pressure gas through the regenerator and into the cold displacement volume. The high pressure valve to the displacer is typically closed before the displacer reaches the top, and the gas partially expands when the displacer reaches the top. The displacer's low pressure valve is then opened and the expanded gas is cooled. The pressure above the drive stem then switches to high pressure, pushing the displacer down and forcing the cooled low pressure gas through the cold end heat exchanger and out again through the regenerator to complete the cycle. When the pressure on the displacer switches, the pressure drop across the regenerator creates a force in the same direction as the force on the drive stem. When the pressure-displacement relationship, PV, is plotted in a diagram, the order of the relationship is clockwise and the area is equal to the amount of cooling that occurs in one cycle. When the rotary valve of U.S. Pat. As a result, cooling efficiency decreases. During phases of the cycle where the pressure within the displacer and the pressure on the drive stem are the same, no net force is generated to move the displacer.

U.S. Pat. No. 8,448,461 to Longsworth discloses a pneumatically driven Brayton cycle expander having a stem on a displacer/piston that uses the mechanism of the invention to move from a cooling cycle to a heating cycle. You can switch to . The mechanism of the present invention can also be used to adjust the orifice that controls the rate at which the displacer/piston moves up and down to optimize cooling during cool-down. While most Brayton cycle expanders have a piston with a seal that separates the cold displaced volume from the warm end, U.S. Pat. It equalizes the pressure of the warm displacement volume and the cold displacement volume, and can therefore be called a displacer.

In order to reverse the expander rotation and increase temperature, the displacer must be at or near the top when the pressure switches from low to high pressure and remain there despite the downward force of the regenerator pressure drop. , it is necessary to ensure that the cold displacement volume is heated by the gas compressed therein. This high pressure hot gas is forced through the regenerator and the pressure switches to low pressure as the displacer descends. This has been accomplished with a Scotch Yoke driven displacer having a rotary valve as described in US Pat. No. 5,361,588 by Asami. In the Scotch yoke drive, the position of the displacer is fixed by rotating the motor regardless of the pressure. When the displacer rotates in the forward direction, the timing of gas inflow and outflow through the valve is optimized to generate refrigeration. The rotary valve disc is rotated by a valve motor having a shaft with a surface that slides over ports in the valve seat and a pin that engages a slot in the back of the valve disc. The valve disc of US Pat. No. 5,361,588 has an annular slot that changes the angle at which the pin engages the slot. This causes the high pressure port to open when the displacer is at the top and moves to the bottom, and the low pressure port to open when the displacer is at the bottom and moves to the top. The PV sequence is counterclockwise. Valve timing is to achieve a near-optimal heating cycle.

Increasing the cooling capacity of the expander to cool large cryopumps makes the Scotch yoke drive much larger and more expensive than the pneumatic drive, so a more efficient pneumatic drive that can change from a cooling cycle to a heating cycle is recommended. An expander is required.

US Pat. No. 7,191,600 to Gao and Longsworth discloses a pulse tube expander having separate rotary valves for flow to the regenerator and flow to the pulse tube. When the valve motor is rotating in the forward direction, the phase difference between the two valves causes cooling, and when the valve motor is rotating in the opposite direction, the phase shift between the two valves causes a rise in temperature. let International Publication WO 2018/168305 discloses a different valve configuration for a pulse tube expander than that described in US Pat. No. 7,191,600, which causes a temperature increase upon rotation in the opposite direction.

The principle of U.S. Patent No. 5,361,588 is that the Scotch yoke, which is the mechanism that drives the displacer up and down, is made independent from the rotary valve, which is the valve that switches the pressure to the displacer. It is said to be shifted. International publication WO 2018/168304 discloses a pneumatic drive of a displacer having a piston attached to the drive stem and larger than the drive stem, the piston having different inlet and outlet valves than the valves connected to the displacer. connected to the valve. The valve is a concentric valve disc that slides over a fixed valve seat. The inner valve disc switches flow to the displacer and the outer valve disc switches flow to the top of the drive piston. Reverse rotation of the valve motor causes the outer valve disc to rotate at an angle relative to the inner valve disc, providing the necessary phase shift to provide heating rather than cooling. 8a to 8d respectively show FIG. 1, FIG. 8(a), FIG. 8(c), and FIG. 9(c) of the '304 application. As shown in Figure 8a, gas on the backside of the drive piston in volume 48 is trapped between the drive piston and drive stem seals 50, 32. This circulates around an average pressure that depends on the volume 48. To achieve the rectangular PV diagram shown in FIG. 8c, the volume 48 must be at least twice as large as the volume above the drive piston 46. Figure 8b shows that valves V3 and V4, which control flow to the drive stem, open 180 degrees apart and remain open for the same amount of time, while valve V2 opens approximately 100 degrees after V1 and remains open for the same amount of time. It shows that it remains the same. This asymmetry may provide optimal timing for cooling, but the timing for heating becomes suboptimal, as reflected as the small PV diagram shown in Figure 8d. An important aspect of the present invention is that the opening and closing timings of the valves corresponding to the drive stems can be varied when switching from cooling to heating.

The purpose of the present invention is to switch from cooling to heating without reversing the direction of the drive motor in a pneumatically driven GM type expander, and to provide efficient valve timing for both cooling and heating. It is to be. The displacer of the expander is reciprocated by a drive piston that can be driven to the end of its stroke regardless of the pressure on the displacer, and a rotary valve with separate tracks is used to switch the pressure between the displacer and the drive piston. High efficiency in both cooling and heating is achieved by providing an independent switching valve that changes flow from the port to the second port for heating. The switching valve can be operated by either a linear drive or a rotary drive. The drive piston can be single-acting or double-acting, and the actuator is connected to a controller that not only switches the flow to the drive piston, but also changes the pressure drop through a switching valve to adjust the speed at which the displacer moves up and down. can also be controlled.

These advantages can be achieved by a cryogenic expander for receiving gas from a compressor at a first pressure and returning gas at a second pressure. The cryogenic expander includes a pneumatically driven, reciprocating displacer assembly and a valve assembly capable of providing cooling and heating modes to provide cooling and heating, respectively. The displacer assembly includes a displacer that reciprocates between a hot end and a cold end within the displacer cylinder, a drive stem attached to the hot end of the displacer and extending through a stem sleeve, and a drive piston having an upper part and a lower part. , the lower part of the drive piston is attached to the upper end of the drive stem, and the drive piston reciprocates within the drive piston cylinder. The drive piston may have a larger diameter than the drive stem. Gas flows between a warm displaced volume and a cold displaced volume through a regenerator. The valve assembly includes a valve seat and a valve disc that rotates over the valve seat. The valve seat has a port located at a first radius that connects to the displacer cylinder or valve actuator, a port located at a second radius that connects to the drive piston cylinder, and a central port that connects to the compressor at a second pressure. has. The valve disc has slots that alternately connect gas at a first pressure and a second pressure to ports located at the first radius and ports located at the second radius. The ports located at the second radius include a cooling port and a heating port. The direction of rotation of the valve disc is constant. The valve assembly further includes a switching valve between the port located at the second radius and the upper volume above the drive piston. The switching valve is configured to connect either the cooling port or the heating port to the upper volume above the drive piston to provide either a cooling mode or a heating mode.

The drawings depict one or more implementations of the present concepts by way of illustration only and not by way of limitation. In the figures, like reference numbers refer to identical or similar elements.

FIG. 1 is a schematic diagram of a cryogenic refrigeration system 100 with a pneumatically actuated GM cycle expander having a single-acting drive piston, a rotary valve, and a switching valve, and is supplied with gas from a compressor via interconnecting piping. FIG. 2 is a schematic diagram of a cryogenic refrigeration system 200 with a pneumatic GM cycle expander having a double-acting drive piston, a rotary valve, and a switching valve, and is supplied with gas from a compressor via interconnecting piping. FIG. 3 is a schematic diagram of a cryogenic refrigeration system 300 with a pneumatically operated Brayton cycle expander having a single-acting drive piston, a rotary valve, and a switching valve, and is supplied with gas from a compressor via interconnecting piping. 1 is a cross-sectional view of the rotary valve, switching valve, and drive piston of system 100. FIG. 2 is a cross-sectional view of the rotary valve, switching valve, and drive piston of system 200. FIG. FIG. 3 shows the pattern of slots in the valve disk superimposed on the valve seat when the displacer of system 100 is being evacuated to low pressure. FIG. 4 illustrates the sequence of slots in the valve disk of system 100 that pass over ports in the valve seat as the valve disk rotates while the expander is cooling. 6b is a PV diagram of the cooling cycle with numbered points on the cycle shown in FIG. 6b; FIG. FIG. 3 illustrates the pattern of slots in the valve disc superimposed on the valve seat when the displacer of system 100 is about to be pressurized to high pressure. FIG. 4 illustrates the sequence of slots in the valve disk of system 100 that pass over ports in the valve seat as the valve disk rotates while the displacer is heating up. 7b is a PV diagram of the temperature ramp cycle with numbered points on the cycle shown in FIG. 7b; FIG. FIG. 1 is a diagram illustrating FIG. 1 of the No. 304 application. FIG. 8A is a diagram showing FIG. 8(a) of the No. 304 application. It is a figure which shows FIG.8(c) of a No. 304 application. It is a figure which shows FIG.9(c) of a No. 304 application.

In this section, some embodiments of the invention will be described in more detail with reference to the accompanying drawings, which illustrate preferred embodiments of the invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments disclosed herein. rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements, and prime notation is used throughout to indicate like elements in alternative embodiments. Identical or similar parts in the drawings are designated by the same reference numerals and descriptions will generally not be repeated.

Cryogenic expanders typically operate with the cold end at the bottom, so terms such as top and bottom and top/bottom refer to this orientation. In the drawings, like numbers are used to refer to like parts, and subscripts are used to distinguish like parts in different configurations.

FIG. 1 shows the central features of the invention, the valve and the drive piston, being transferred to the rest of the system, i.e. the displacer 20a in the cylinder 30, and to the rotary valve 2 via line 16 at a first pressure, i.e. high pressure. 1 is a circuit diagram of a cryogenic refrigeration system 100 shown in detail in relation to a compressor 15 supplying gas at Ph and receiving gas from rotary valve 2 via line 17 at a second pressure, low pressure Pl; FIG. The rotary valve 2 is such that ports on a rotating disk pass through ports on a stationary valve seat. The port located at the first radius 10a on the valve seat circulates gas via line 9 to the hot end of the displacer cylinder 30, and the port located at the second radius 11a circulates the gas through the switching valve 1 and line 18. Gas is circulated through the upper end of the drive piston cylinder 6a. Line 18a originates from the first port located at the second radius 11a of the valve seat, designated as the cooling port, and line 18b begins at the second radius 11a of the valve seat, designated as the heating port. Starting from the second port located. The schematic diagram of the switching valve 1 shows that it is fixed in the position shown during cooling and rotated 90 degrees counterclockwise during heating. The schematic diagram of the rotary valve 2 shows the gas in line 9 connected to the cylinder 30 at high pressure Ph and the gas in line 18 connected to the cylinder 6a at low pressure Pl when the displacer 20a is raised.

The displacer 20a reciprocates between a warm end and a cold end within the cylinder 30, forming a warm displaced volume 25 and a cold displaced volume 26. Gas flows between volumes 25 and 26 through hot end port 23, regenerator 22a, and cold end port 24 of displacer body 21a. Seal 27 prevents gas from bypassing regenerator 22a. The displacer 20a is driven up and down by a drive stem 7, whose lower end is connected to the upper end of the displacer 20a, and its upper end is connected to the lower end of the drive piston 5a. The drive piston 5a is such that the pressure difference between the circulating gas pressure in the upper volume 12a of the drive piston 5a and the pressure in the lower buffer volume 13a of the drive piston 5a acts on the outer region of the drive stem 7. is driven up and down by. The drive piston 5a is called single acting because it is driven only by pressure changing from a high pressure Ph to a low pressure Pl on one side of the piston. A seal 31 in the drive piston 5a separates the gas in volume 12a from the gas in volume 13a. A seal 28 in the stem sleeve 8 separates the gas in volume 13a from the gas in volume 25.

Typical operating pressures are a supply pressure Ph of about 2.2 MPa, a return pressure Pl of about 0.8 MPa, and a pressure ratio of 2.8, so in order for the drive piston 5a to complete a full stroke, the buffer The volume 13a needs to be three times or more the displacement volume 12a. A larger volume is required to reduce the pressure variation in volume 12a so that the pressure difference across the drive piston 5a is approximately constant during the full stroke. This large buffer volume 13a relative to the volume 12a is schematically shown as a separate volume from the volume on the pressure change side below the drive piston 5a.

FIG. 2 shows a schematic diagram of a cryogenic refrigeration system 200 that differs from system 100 in having a double-acting drive piston 5b. The pressure on the lower side of the drive piston 5b is low pressure Pl when the upper pressure is high pressure Ph, and is high pressure Ph when the upper pressure is low pressure Pl. In the system 100, the line 18b from the heating port of the rotary valve 2 is cut off by the switching valve 1 during cooling, but in the system 200, the line 18b from the temperature rising port of the rotary valve 2 is cut off by the switching valve 1 through the switching valve 3 and the line 19. 13b. Since the total pressure difference Ph-Pl acts on the double-acting drive piston 5b, the diameter can be made smaller than that of the single-acting drive piston 5a, and the upper and lower volumes 12b and 13b of the drive piston 5b also change depending on the drive piston 5b. It can be made as small as the volume.

The rotary valve 4 has a port to line 9 at a first radius 10b on the valve seat and a port to lines 18a, 18b and line 18 at a second radius 11b. , similar to rotary valve 2. The switching valve 3 is configured such that when the gas from the cooling line 18a is connected to the line 18, the gas from the temperature raising line 18b of the rotary valve 4 is connected to the line 19, whereby the rotation of the valve disk 4 is Accordingly, the pressure above and below the drive piston 5b is switched to the opposite pressure.

The switching valve 3 is fixed at the illustrated position during cooling, and is rotated 90 degrees counterclockwise when the temperature is rising. In the schematic diagram of the rotary valve 4, when the displacer 20a is raised, gas in the line 9 connected to the cylinder 30 at high pressure Ph, gas in the line 18 connected to the upper part of the cylinder 6b at low pressure Pl, and gas in the cylinder 30 at high pressure Ph. 6b, and a line 19 connected to the lower part of the gas line 6b. The mechanism for shifting a pneumatically driven cryogenic expander from cooling to heating is ideal for cryopumps cooled by GM cycle expanders, but as shown in Figure 3, it is applicable to pneumatically driven Brayton cycle expanders. It is also possible to do so.

FIG. 3 is a schematic diagram of a cryogenic refrigeration system 300 that includes a pneumatically operated Brayton cycle expander with a single-acting drive piston. The Brayton cycle expander of system 300 has a main inlet valve 9a and outlet valve 9b at the cold end of cylinder 30b. Gas flows from compressor 15 through high pressure line 16 and heat exchanger 50 to inlet valve 9a, and from outlet valve 9b back through heat exchanger 50 and low pressure line 17. The displacer 21b includes a regenerator 22b, which circulates gas from the cold end volume 26 to the hot end volume 25 to maintain substantially the same pressure above and below the displacer 21b, and the regenerator 22b circulates gas from the cold end volume 26 to the hot end volume 25 to maintain substantially the same pressure above and below the displacer 21b. Cooling or heating can be achieved using a drive piston mechanism. The port located at the first radius 10c of the rotary valve 2' is relatively small as it only circulates a small amount of gas to the pneumatic actuators 29a, 29b which open and close the cold inlet valve 9a and the cold outlet valve 9b. The pneumatic actuator 29a opens the valve 9a when connected to the high pressure Ph, and closes the valve 9a when connected to the low pressure Pl. The same applies to the actuator 29b and the valve 9b.

FIG. 4 shows a cross section of the switching valve 1, the rotary valve 2, and the drive piston 5a of the system 100. The rotating disk 2a is rotated by a valve motor 40, a motor shaft 41, and a pin 42 that engages a slot 44 in the top of the disk 2a. The valve disc illustrated for the present invention has two cycles per revolution and therefore has two symmetrical high and low pressure slots. The valve seat has two sets of symmetrical ports for flow to the displacer, but can also have only one pair of ports for flow to the drive piston. The lower part of the valve disc 2a abuts the valve seat 2b, and a slot 17a shown here connects the low pressure return port 17 with a line 18a to the piston drive volume 12a via the spool 1b. This is the cooling mode. System 100 switches to heating mode when linear actuator 1a pulls spool 1b to the right and line 18b is connected to piston drive volume 12a. Lines 18a and 18b may have different flow impedances, which allows the drive piston 5a to move up and down at different speeds in heating and cooling modes. Different flow impedances may be determined by the opening of the switching valve or by a fixed port size. The piston speed may be controlled by controlling the opening of the switching valve.

The switching valve 1 has only the cooling port 18a in fluid communication with the upper volume 12a above the drive piston 5a when the expander is in the cooling mode, and only the heating port 18b is actuated when the expander is in the heating mode. It may be configured to be in fluid communication with the upper volume 12a above the piston 5a. The linearly operating actuator 1a may be configured to control the pressure loss through the switching valve 1 to control the speed at which the displacer 20a moves up and down.

FIG. 5 shows a cross section of the switching valve 3, rotary valve 4 and drive piston 5b of the system 200. The bottom surface of the valve disc 4a is in contact with the valve seat 4b, the slot 16a connects the high pressure supply port 16 and line 18b to the piston drive volume 12b via the spool 3b and the line 18, and the slot 17a connects the piston drive volume 12b via the spool 3b and the line 18. and line 19 connects low pressure return port 17 and line 18a to piston drive volume 13b. This is the heating mode. System 200 switches to cooling mode when rotary actuator 3a rotates spool 3b 90 degrees, line 18a connects to piston drive volume 12b, and line 18b connects to piston drive volume 13b.

Figures 6a and 7a exemplarily show the rotary valve of the system 100-300 in two positions. Figure 6b when cooling and Figure 7b when heating up show the timing of the high and low pressure slots of the valve disk passing through the ports of the valve seat, which correspond to opening and closing of the valve. FIGS. 6c and 7c show the opening and closing of the valves on the PV diagram during cooling and heating. Figures 6a and 7a show the slots 16a, 17a of the valve disc 2a as seen from the valve motor, in a plane that rotates counterclockwise relative to the valve seat 2b. The port 9 of the valve seat 2b located at the first radius 46 connects to the displacer cylinder 30 and opens as a valve V1 (see Figure 6b) when the high pressure slot 16a passes over it and the low pressure slot 17a connects to the displacer cylinder 30. When passing through, the low pressure valve V2 is opened. The lines 18a, 18b of the valve seat 2b located at the second radius 45 connect to the upper part of the drive piston cylinder 6a and open as valves V3a, V3b when the high pressure slot 16a passes over them, and the low pressure slot 17a When passing over these, the low pressure valves V4a and V4b are opened. The switching valve 1 cuts off the flow from the line 18b when the expander is being cooled, and cuts off the flow from the line 18a when the expander is rising in temperature.

Figures 6a, 6b, 6c show a cooling cycle starting at the end of the expansion phase, with the cold displaced volume 26 at its maximum, the displacer 20a at the top, and the pressure greater than the low pressure Pl. . Numbers 1 to 8 in Figures 6b and 6c indicate the valve timing and the corresponding PV cycle, which is summarized as follows.

1: Valve V2 opens and the pressure inside the displacer drops to low pressure Pl.

2: After the pressure drops to Pl, V3a opens and the displacer is pushed toward the bottom by the pressure difference above and below the drive piston.

3: V2 closes before the displacer reaches the bottom, cold gas moves to the warm end, pressure increases, and the displacer moves the rest of the way to the bottom.

4: V1 opens and the pressure rises to high pressure Ph.

5: V3 closes.

6: V4 opens and the displacer is pushed upwards by the pressure difference on the drive piston.

7: V1 closes before the displacer reaches the top, the warm gas moves to the cold end, the pressure decreases, and the displacer moves the rest of the way to the top.

8: V4 closes.

This cycle has two principles: the first principle is that the drive piston pressure switches after the displacer pressure switches, and the second principle is that the displacer reaches the upper and lower stroke ends. This means that valves V1 and V2 are closed before.

Figures 7a, 7b and 7c show a heating cycle starting from the beginning of the low pressure phase, with the displacement volume 26 being minimal, the displacer 20a at the bottom and the pressure being greater than the low pressure Pl. Numbers 1-8 in Figures 7b and 7c indicate the valve timing and the corresponding PV cycle, which is summarized as follows.

1: Valve V2 opens and the pressure inside the displacer drops to Pl. Note that the valve V3b is still open, maintaining high pressure gas above the drive piston 5a, and maintaining the drive piston 5a downward.

6: After the pressure drops to Pl, V4b opens and the displacer is drawn toward the top due to the pressure difference above and below the drive piston.

3: V2 closes before the displacer reaches the top, warm gas moves to the bottom, pressure increases, and the displacer moves the rest of the way to the top.

4: V1 opens and the pressure rises to high pressure Ph. Note that V4b is still open, allowing the drive piston to keep the displacer on top.

7: V1 closes, the displacer moves to the bottom, the pressure decreases, and the gas moves from the cold end to the warm end.

This cycle has three principles. The first principle is that when valves V1 and V2 switch pressure, the pressure above the drive piston holds the displacer up or down. The second principle is to switch the pressure above the drive piston after reaching the high or low pressure, and the third principle is to close the valves V1 and V2 before the displacer reaches the top or bottom. Here, since the temperature raising line 18b can be placed at a position more than 90 degrees away from the cooling line 18a, even if the cooling cycle is optimized by opening V2 longer than V1 and opening V1 more than 90 degrees after V2, It is important that there is no adverse effect on the thermal cycle.

The valve opening and closing timing for system 300 may be the same as for system 100. In this case, since it is necessary to switch the upper and lower pressures of the drive piston 5b simultaneously, the valves of the system 200 and the valve opening/closing timing are more symmetrical. Therefore, a compromise is necessary to balance a good cooling cycle with a good heating cycle.

The claims are not limited to the specific elements recited. For example, the switching valve 1 shown as operating linearly can be replaced by a valve operating rotationally. The heating port located at the second radius may alternatively be located at the third radius. It is also within the scope of these claims to include suboptimal operating limits to simplify mechanical design. The terms and descriptions used herein are for illustrative purposes only and are not intended to limit the invention. It will be apparent to those skilled in the art that many modifications may be made within the spirit and scope of the invention and the embodiments described herein.

1 Switching valve 1a Linear actuator 1b Spool 2 Rotary valve 3 Switching valve 3a Rotary actuator 3b Spool 4 Rotary valve 4a Valve disc 4b Valve seat 5a Drive piston 5b Drive piston 6a Drive piston cylinder 6b Drive piston cylinder 7 Drive stem 8 Stem sleeve 9 Line 9a Inlet valve 9b Outlet valve 10a First radius 10b First radius 11a Second radius 11b Second radius 12a Volume 12b Volume 13a Buffer volume 13b Volume 15 Compressor 16 Line 16a Slot 17 Line 17a Slot 18 Line 18a Line 18b Line 20a Displacer 20b Displacer 21a Displacer body 21b Displacer body 22a Regenerator 22b Regenerator 23 Hot end port 24 Cold end port 25 Volume 26 Volume 27 Seal 28 Seal 29a Pneumatic actuator 29b Pneumatic actuator 30 Cylinder 30b Cylinder 31 Seal 40 Valve motor 41 Motor shaft 42 Pin 44 Slot 45 Second radius 46 First radius 50 Heat exchanger 100 Cryogenic refrigeration system 200 Cryogenic refrigeration system 300 Cryogenic refrigeration system

Claims (14)

A cryogenic expander that receives gas from a compressor at a first pressure and returns gas at a second pressure, the cryogenic expander comprising:
a pneumatically driven reciprocating displacer assembly;
a valve assembly capable of providing a cooling mode and a heating mode that produce cooling and heating, respectively;
Equipped with
The displacer assembly includes:
A displacer that reciprocates between a hot end and a cold end of the displacer cylinder within a displacer cylinder, the displacer generating a warm displacement volume and a cold displacement volume within the displacer cylinder, and causing the gas to warm up through a regenerator. the displacer flowing between the cold displacement volume and the cold displacement volume;
a drive stem attached to the hot end of the displacer and extending through a stem sleeve;
a drive piston having an upper part and a lower part, the lower part of the drive piston being attached to the upper end of the drive stem and reciprocating within a drive piston cylinder, the drive piston having a larger diameter than the drive stem; the drive piston separating an upper volume above the drive piston and a lower volume below the drive piston;
Equipped with
The valve assembly includes:
a valve seat, the valve seat having a port located at a first radius that connects to the displacer cylinder or valve actuator, a port located at a second radius that connects to the drive piston cylinder, and a port located at a second radius that connects to the drive piston cylinder; the valve seat having a central port connecting to the compressor at pressure;
a valve disk rotating above the valve seat, the valve disk directing the gas at the first pressure and the second pressure to ports located at the first radius and the second radius; the valve disk comprising alternately connected slots, the port located at the second radius comprising a cooling port and a heating port, and the rotation direction of the valve disk is constant;
a switching valve provided between the port located at the second radius and the upper volume above the drive piston; the switching valve connected to the volume and configured to provide either the cooling mode or the heating mode;
A cryogenic expander characterized by comprising: The switching valve connects the heating port to the lower volume below the drive piston when the expander is in the cooling mode, and connects the heating port to the lower volume below the drive piston when the expander is in the heating mode. 2. The cryogenic expander of claim 1, wherein the cryogenic expander is configured to connect to the lower volume below the drive piston. The switching valve connects the cooling port to the upper volume above the drive piston when the expander is in the cooling mode, and connects the heating port to the upper volume above the drive piston when the expander is in the heating mode. 3. The cryogenic expander of claim 2, wherein the cryogenic expander is configured to connect to the upper volume above the drive piston. 3. The switching valve comprises a spool configured to rotationally switch the connection of the heating port and the cooling port to the lower volume below the drive piston. cryogenic expander. The switching valve is configured such that when the expander is in the cooling mode, only the cooling port is in fluid communication with the upper volume above the drive piston, and when the expander is in the heating mode, the cooling port is in fluid communication with the upper volume above the drive piston. 2. The cryogenic expander of claim 1, wherein only a heating port is configured to be in fluid communication with the upper volume above the drive piston. 6. The switching valve includes a spool configured to linearly switch communication between the cooling port and the heating port with the upper volume above the drive piston. Cryogenic expander. 6. The cryogenic expander of claim 5, wherein lines connecting the cooling port and the heating port, respectively, to the upper volume above the drive piston have different flow impedances. The switching valve is
a spool for connecting either the cooling port or the heating port to the upper volume above the drive piston;
an actuator for linearly or rotationally operating the spool;
The cryogenic expander according to claim 1, comprising: 9. The cryogenic extract of claim 8, wherein the linearly actuated actuator is configured to control the pressure drop across the switching valve to control the speed at which the displacer moves up and down. Panda. 10. The cryogenic expander of claim 9, wherein the actuator that operates linearly is configured to control the opening of the switching valve to control the pressure drop. The displacer is placed at the hot end or the cold end of the displacer cylinder until the pressure reaches the first pressure or the second pressure before the displacer moves toward the other end during cooling and heating. A cryogenic expander according to claim 1, characterized in that the cryogenic expander remains stationary. The cryogenic expander of claim 1, wherein the port located at the first radius is connected to the warm displacement volume of the displacer cylinder. The displacer assembly further includes a cold inlet valve and a cold outlet valve connected to the cold displacement volume of the displacer cylinder;
the port located at the first radius is connected to the valve actuator;
the valve actuator comprises a first valve actuator that opens the inlet valve when connected to the first pressure of the compressor;
The cryogenic expander of claim 1, wherein the valve actuator comprises a second valve actuator that opens the outlet valve when connected to the first pressure of the compressor. 2. The cryogenic expander of claim 1, wherein the heating port is located closer to one of the ports located at the first radius than the cooling port.

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